It has been common practice in the electronic field to contain different functional units of an electronic system in a plurality of separate housings. The functional units in each of the housings are then interconnected by connection lines external to the housings to form the electronic system. Typically, the housings are designed in modular shape and size (e.g., modules) such that they can be mass produced. The modular shape and size of the housings also make it possible for the modular housings to be stacked on one another.
One typical example of such a modular electronic system is the modular audio and/or video component system. A typical audio component system includes an amplifier component, a preamplifier component, an AM-FM radio component, a CD (i.e., compact disk) player component, a cassette player component, and a record player component. These components are typically contained in separate modular housings and are stacked on one another. Another example of such a modular electronic system is the modular computer system. A typical modular computer system includes a central computer unit contained in a modular housing, and a plurality of peripheral devices in a plurality modular housings. These modules may then be stacked together.
One advantage of the modular system is that the system does not need to reserve space for future expansion inside each component. Each modular component of the system includes minimum circuitry for the designated function of the component, and an interface circuit for communications with other components of the system. The system can function with only core modular components of the system. When the expansion of the system is needed to enhance the operational features or to provide with more functions of the system, expansion components which are also in modular form can be added to the system. For example, when additional storage is required in a modular computer system, storage expansion components, such as a disk drive, an optical storage drive, a tape drive, or additional memory can then be employed to connect to the computer system via connection lines as these expansion components are all contained in separate modular housings. In this way, the computer system can be minimum equipped under its current operating conditions. When additional functions or features are needed, the computer system can be easily expanded by adding additional component modules or replacing the existing component modules with more advanced modules.
In order to make the external connection lines of the modular system simple and short and to allow the modular system to occupy minimum surface space, the component modules in the modular system are typically stacked together.
Disadvantages, however, are associated with the stacking arrangement for the modular systems. One disadvantage associated is that the stacked component modules may be moved horizontally away from its stacked position by external force and fall off, thus damaging the electronic circuitry inside the modules.
A number of prior art approaches are known for solving this problem. One such prior art approach is shown and described in U.S. Pat. No. 4,718,858, which shows and describes stackable housings for electronic units. Each of the stackable housings includes L-shaped front feet and stacking feet on the bottom surface. Each of the stackable housings also includes, on its top surface, top securing holes (boot-shaped) for the L-shaped front feet and stacking notches for the stacking feet. When one of the stackable housings is stacked on another one of the stackable housings, the front portions of the stacked units are secured by the L-shaped feet on the stacked unit retained in the securing holes and the rear portions of the stacked units are secured by the stacking feet of the stacked unit engaging the stacking notches on the base unit.
Another prior art approach is shown and described in U.S. Pat. No. 4,838,422, which describes data storage containers that can be stacked together securely. Each of the containers has tapered parallel protruding rails on the bottom surface which lie opposite each other. Each of the containers also includes parallel rail members positioned opposite each other on the top surface of each container. The parallel members each includes an angled surface. When two of the containers are stacked together, the bottom tapered parallel rail members of the upper container are frictionally engaged via sliding with rail members of the lower container, thus securing the upper container.
One disadvantage of these prior art approaches is that they typically require extra effort to stack one stackable housing/container on top of another one securely. Similarly, extra effort is also required to remove one of the stackable housings/containers from its stacked position.